Generally, in a lens barrel of an imaging apparatus of various types, such as a video camera and a still camera, an optical element, such as a lens, disposed inside the lens barrel. For example, by rotationally operating an operation ring or an operation knob provided at the outer peripheral side, the lens, for example, is shifted in the optical-axis direction so that the zoom magnification can be changed or focusing can be performed. Moreover, information, such as a photographing distance and a focal length, is calculated from the positional information of, for example, the lens and is used for, for example, controlling exposure and strobe light. Therefore, proper detection of the rotation amount of the operation ring is important.
For example, in order to properly control the zoom magnification by rotating the operation ring, it is necessary to properly ascertain the rotational position of the operation ring by detecting the rotation amount of the operation ring provided at the lens barrel.
Patent Literature 1 discloses a technology for detecting the position of the operation ring by using a reflective sensor (photo-reflector) to detect a difference in intensities of light reflected by a reflective surface.
Patent Literature 2 discloses a technology for detecting the rotation amount (movement amount) by using a reflective sensor (photo-reflector) to detect a difference in intensities of light reflected by a reflective member (reflective sheet) having a reflective portion and a non-reflective portion.